1. Field of the Invention
This invention relates to an X-ray detector, and more particularly to an X-ray detecting device and a fabricating method thereof that is capable of preventing a contact badness among a drain electrode, a ground electrode and a transparent electrode.
2. Description of the Related Art
Generally, an X-ray imaging system photographing an object using a non-visible light ray such as an X-ray, etc. has been used for medical, science and industry applications. This X-ray imaging system includes an X-ray detecting panel for detecting an X-ray passing through an object to convert it into an electrical signal.
As shown in FIG. 1, the X-ray detecting panel includes a photo sensitive layer 6 for detecting an X-ray, and a thin film transistor substrate for switching and outputting the detected X-ray from the photo-sensitive layer 4. The thin film transistor substrate includes pixel electrodes 34 arranged in a pixel unit, and thin film transistors (TFT""s), each of which is connected to a charging capacitor Cst, a gate line 2 and a data line (not shown) On the upper portion of the photo sensitive layer 4 is provided a dielectric layer 6 and an upper electrode 8 which is connected to a high voltage generator 10. The photo sensitive layer 4 made from a selenium with a thickness of hundreds of xcexcm detects an incident X-ray to convert it into an electrical signal. In other words, the photo sensitive layer 4 produces an electron-hole pair when an X-ray is incident thereto, and separates the electron-hole pair when a high voltage of several kV is applied from the high voltage generator 10 to the upper electrode 8. The pixel electrode 34 plays a role to charge holes produced by X-ray detection from the photo sensitive layer 6 into the charging capacitor Cst. The thin film transistor (TFT) responds a gate signal inputted over the gate line 2 to apply a voltage charged in the charging capacitor Cst to the data line. Pixel signals supplied to the data line is applied, via a data reproducer, to a display device, thereby displaying a picture.
Referring to FIG. 2 and FIG. 3, in the thin film transistor substrate, the pixel electrode 34 is formed at a unit pixel area defined by the gate line 2 and a data line 42. The charging capacitor Cst is formed by the pixel electrode 34 and a transparent electrode 30 positioned at the lower portion of the pixel electrode 34 with having a storage insulation layer 32 therebetween. A ground electrode 20 is formed in a direction crossing the pixel electrode 34 to reset the residual electric charges of the charging capacitor Cst. The ground electrode 34 is electrically coupled, via a ground contact hole 26b, to the transparent electrode 30.
The thin film transistor (TFT) is formed at an intersection between the data line 42 and the gate line 3. The TFT consists of a gate electrode 36 extended from the gate line 2, a source electrode 38 extended from the data line 42, a drain electrode 40 connected, via drain contact holes 24a, 26a and 28a, to the pixel electrode 34, and semiconductor layers 14 and 16 for defining a conductive channel between the source electrode 38 and the drain electrode 40.
FIG. 4A to FIG. 4h shows a method of fabricating the X-ray detecting device shown in FIG. 2 step by step.
Referring first to FIG. 4A, the gate electrode 36 and the gate line 2 are provided on the substrate 1.
The gate electrode 36 and the gate line 2 are formed by depositing a metal material using a deposition technique such as a sputtering, etc. to form a conductive layer and then patterning the conductive layer. The gate electrode 36 and the gate line 2 are formed from a metal material such as an aluminum ally, and are preferably formed from aluminum-neodymium/molybdenum (AlNd/Mo).
Referring to FIG. 4B, an active layer 14 and an ohmic contact layer 16 are provided on a gate insulating film 12.
The gate insulating film 12 is formed by entirely depositing an insulating material, such as silicon nitride (SiNx) or silicon oxide (SiOx), onto the substrate 1 by the plasma enhanced chemical vapor deposition (PECVD) technique in such a manner to cover the gate line 2 and the gate electrode 36.
The active layer 14 and the ohmic contact layer 16 are formed by sequentially disposing first and second semiconductor material layers 14 and 16 on the gate insulating film 12 and then patterning them. The active layer 14 is formed from a first semiconductor material, that is, amorphous silicon that is not doped with an impurity. On the other hand, the ohmic contact layer 16 is formed from a second semiconductor material, that is, amorphous silicon doped with an n-type or p-type impurity at a high concentration.
Referring to FIG. 4C, the data line 42, the ground electrode 20, the source electrode 38 and the drain electrode 40 are provided on the gate insulating film 12.
The data line 42, the ground electrode 20 and the source and drain electrodes 38 and 40 are formed by depositing a metal material using the CVD technique or the sputtering technique and then patterning the metal material. After the source and drain electrodes 38 and 40 were patterned, the ohmic contact layer 16 at an area corresponding to the gate electrode 36 also is patterned to expose the active layer 14. A portion of the active layer 14 exposed by the source and drain electrodes 38 and 40 serves as a channel. The data line 42, the ground electrode 20, and the source and drain electrodes 38 and 40 are made from chrome (Cr) or molybdenum (Mo).
Referring to FIG. 4D, a first protective layer 18 are provided on the gate insulating layer 12.
The first protective layer 18 is formed by depositing an inorganic insulating material on the gate insulating layer 12 in such a manner to cover the data line 42, the ground electrode 20 and the source and drain electrodes 38 and 40 and then patterning it. The first protective layer 18 is preferably made from silicon nitride (SiNx) or silicon oxide (SiOx), etc.
The first protective layer is provided with a first ground contact hole 24b and a first drain contact hole 24a. The ground electrode 20 is exposed by the first ground contact hole 24b passing through the first protective layer 18. The drain electrode 40 is exposed by the first drain contact hole 24a passing through the first protective layer 18.
Referring to FIG. 4E, an organic insulating layer 22 are provided on the first protective layer 18. The organic insulating layer 22 is formed by depositing an organic insulating material, such as an acrylic organic compound, Teflon, BCB (benzocyclobutene), Cytop or PFCB (perfluorocyclobutane), etc., on the first protective layer 18 and then patterning it.
This organic insulating layer 22 is provided with a second drain contact hole 26a and a second ground contact hole 26b. Each of the second drain contact hole 26a and the second ground contact hole 26b has a width smaller than each of the first drain contact hole 24a and the first ground contact hole 24b. The drain electrode 40 is exposed by the second drain contact hole 26a passing through the organic insulating layer 22. The ground electrode 20 is exposed by the second ground contact hole 26b passing through the organic insulating layer 22.
Referring to FIG. 4F, a transparent electrode 30 is provided on the organic insulating layer 22.
The transparent electrode 30 is formed by depositing a transparent conductive material onto the organic insulating layer 22 and then patterning the deposited transparent conductive material. The transparent electrode 30 is made from a transparent material such as indium-tin-oxide (ITO), indium-zinc-oxide (IZO) or indium-tin-zinc-oxide (ITZO).
The transparent electrode 30 is electrically connected, via the second drain contact hole 26a, to the drain electrode 40 while being electrically connected, via the second ground contact hole 26b, to the ground electrode 20.
Referring to FIG. 4G, a second protective layer 32 is provided on the organic insulating layer 22.
The second protective layer 32 is formed by depositing an insulating material such as silicon nitride (SiNx) or silicon oxide (SiOx) and then patterning it in such a manner to cover the transparent electrode 30.
The second protective layer 32 is provided with a third drain contact hole 28a and a third ground contact hole 28b. Each of the third drain contact hole 28a and the third ground contact hole 28b has a width smaller than each of the second drain contact hole 26a and the second ground contact hole 26b. The transparent electrode 30 is exposed by the third drain contact hole 28a passing through the second protective layer 32.
Referring to FIG. 4H, the pixel electrode 34 is provided on the second protective layer 32.
The pixel electrode 34 is formed by depositing a transparent conductive material on the second protective layer 32 and then patterning the deposited transparent conductive material.
The pixel electrode 34 is electrically connected, via the first to third drain contact holes 24a, 26a and 28a, to the drain electrode 40. The pixel electrode 34 is made from a transparent conductive material such as indium-tin-oxide (ITO), indium-zinc-oxide (IZO) or indium-tin-zinc-oxide (ITZO).
In the X-ray detecting device as described above, when the organic insulating material 22 is formed by the photolithography including a dry etching after the ground electrode 20 and the drain electrode 40 were formed from chrome (Cr), the contact holes 24a and 24b are defined to expose the ground electrode 20 and the drain electrode 40. The ground electrode 20 and the drain electrode 40 are electrically connected, via the contact holes 24a and 24b, to the transparent electrode 30.
However, when the organic insulating material 22 is formed by the photolithography including a dry etching after the ground electrode 20 and the drain electrode 40 were formed from molybdenum (Mo), the ground electrode 20 and the drain electrode 40 also are over-etched to have a difficulty in setting a dry etching condition of the organic insulating layer 22. This causes a drawback in that only the side surfaces of the over-etched ground and drain electrodes 20 and 40 should be in contact with the transparent electrode 30, to thereby generate a contact badness.
Accordingly, it is an object of the present invention to provide an X-ray detecting device and a fabricating method thereof that is capable of preventing a contact badness among a drain electrode, a ground electrode and a transparent electrode.
In order to achieve these and other objects of the invention, an X-ray detecting device according to one aspect of the present invention includes an auxiliary electrode formed on a substrate simultaneously with a gate electrode; a drain electrode electrically connected to the auxiliary electrode; and a transparent electrode electrically connected, via a contact hole passing through the drain electrode, to the auxiliary electrode.
The X-ray detecting device further includes a gate insulating film formed in such a manner to cover the auxiliary electrode; a semiconductor layer formed in such a manner to correspond to the auxiliary electrode and the gate electrode; and a contact hole passing through the gate insulating film and the semiconductor layer to expose the auxiliary electrode.
In the X-ray detecting device, the auxiliary electrode is formed from aluminum-neodymium/molybdenum (AlNd/Mo). The drain electrode is formed from molybdenum (Mo).
Meanwhile, the X-ray detecting device further includes an auxiliary electrode formed simultaneously with the gate electrode; a ground electrode electrically connected to the second auxiliary electrode; and a transparent electrode electrically connected, via a contact hole passing through the ground electrode, to the auxiliary electrode.
The X-ray detecting device further includes a gate insulating film formed on the substrate in such a manner to cover the auxiliary electrode; a semiconductor layer formed on the gate insulating film; and a cont passing through the gate insulating film and the semiconductor layer to expose the auxiliary electrode.
In the X-ray detecting device, the auxiliary electrode is formed from aluminum-neodymium/molybdenum (AlNd/Mo). The ground electrode is formed from molybdenum (Mo).
A method of fabricating an X-ray detecting device according to another aspect of the present invention includes the steps of forming an auxiliary electrode on a substrate simultaneously with a gate electrode; forming a gate insulating film on the substrate in such a manner to cover the gate electrode and the auxiliary electrode; forming a semiconductor layer on the gate insulating film; forming a first contact hole passing through the semiconductor layer and the gate insulating film to expose the auxiliary electrode; and forming a source electrode on the gate insulating film and simultaneously forming a drain electrode opposed to the source electrode and electrically connected to the auxiliary electrode.
The fabricating method further includes the steps of forming a first protective layer on the gate insulating film in such a manner to cover the source and drain electrode; forming an insulating layer on the first protective layer; forming a second contact hole passing through at least one of the insulating layer and the drain electrode; forming a transparent electrode electrically connected, via the second contact hole, to at least one of the drain electrode and the auxiliary electrode; forming a second protective layer on the insulating layer; and forming a pixel electrode electrically connected to the transparent electrode on the second protective layer.
In the method, the insulating layer is made from an organic insulating material. The first and second protective layers are made from an inorganic insulating material. The auxiliary electrode is formed from aluminum-neodymium/molybdenum (AlNd/Mo). The drain electrode is formed from molybdenum (Mo).
Meanwhile, the fabricating method further includes the steps of forming an auxiliary electrode on the substrate simultaneously with the gate electrode; forming a gate insulating film on the substrate in such a manner to cover the auxiliary electrode; forming a semiconductor layer on the gate insulating film; forming a first contact hole passing through the semiconductor layer and the gate insulating film to expose the auxiliary electrode; and forming a ground electrode electrically connected to the auxiliary electrode on the substrate.
The fabricating method further includes the steps of forming a first protective layer on the gate insulating film in such a manner to cover the ground electrode; forming an insulating layer on the first protective layer; forming a second contact hole passing through at least one of the insulating layer and the ground electrode; forming a transparent electrode electrically connected, via the second contact hole, to at least one of the ground electrode and the auxiliary electrode; forming a second protective layer on the insulating layer; and forming a pixel electrode on the second protective layer.
In the fabricating method, the auxiliary electrode is formed from aluminum-neodymium/molybdenum (AlNd/Mo). The ground electrode is formed from molybdenum (Mo). The first and second protective layers are made from an inorganic insulating material. The insulating layer is made from an organic insulating material.